The sperm acrosome reaction must occur to allow release of the acrosomal enzyme to facilitate sperm penetration through the investments surrounding the ova and ultimately to fertilize the ova. The acrosome reaction has been morphologically described in many species and has been shown to be induced by physiological fluids such as follicular fluid. Further induction of the mammalian acrosome reaction has been shown not to be species specific, therefore, results obtained from these studies may readily be extrapolated to other animals including man. There is, however, very little known about the molecular mechanisms of induction of the acrosome reaction. In attempting to understand the molecular mechanism of induction of the acrosome reaction, the following are proposed: 1. Identification and purification of the acrosome reaction inducing factor(s) from ovarian follicular fluid. 2. Isolation of the plasma and outer acrosomal membranes. 3. Purification of protein components in the membranes and identification of those specific to each membrane. 4. Determination of the lipid composition of the isolated membranes. 5. Effects of the purified acrosome reaction inducing factor(s) on the proteins of the plasma and outer acrosomal membranes. 6. Physical and chemical characterization of the acrosomal stabilizing factor from seminal plasma.